Embodiments disclosed herein concern a miniature actuator which is useful in intravascular imaging devices including intravascular ultrasound (IVUS), and optical coherence tomography (OCT). The miniature actuator mechanism and ultrasound or OCT imaging device is preferably embedded in an elongated body such as an intravascular guide wire or catheter to provide imaging guidance in various interventional applications. Description of the Related Art
Coronary artery disease is very serious and often requires an emergency operation to save lives. The main cause of coronary artery disease is the accumulation of plaque inside a person's vasculature, which eventually occludes blood vessels. Several solutions are available, for example, balloon angioplasty, rotational atherectomy, and intravascular stents, to open up the clogged section, which is called stenosis. Traditionally, during the operation, surgeons rely on X-ray fluoroscopic images that are basically planary images showing the external shape of the silhouette of the lumen of blood vessels. Unfortunately, with X-ray fluoroscopic images, there is a great deal of uncertainty about the exact extent and orientation of the atherosclerotic lesions responsible for the occlusion, making it difficult to find the exact location of the stenosis. In addition, though it is known that restenosis can occur at the same place, it is difficult to check the condition inside the vessels after surgery. Intravascular imaging would be valuable during interventional procedures to facilitate navigation and for intraoperative feedback. For example, the precise placement and appropriate expansion of stents would benefit from simultaneous intravascular imaging. Existing intravascular imaging devices are too large and are not flexible enough to be placed simultaneously with other devices.
In order to resolve these issues, an ultrasonic transducer device has been utilized for endovascular intervention to visualize the inside of the blood vessels. To date, the current technology is mostly based on one or more stationary ultrasound transducers or rotating a single transducer in parallel to the blood vessels by means of a rotating shaft which extends through the length of the catheter to a motor or other rotary device located outside the patient. These devices have limitations in incorporating other interventional devices into a combination device for therapeutic aspects. They require a large space inside catheter such that there is not enough room to accommodate other interventional devices. Also, due to the nature of the rotating shaft, the distal end of the catheter is very stiff and it is hard to navigate through tortuous arteries. The high speed rotating shaft also contributes to distorted nonuniform images when imaging a tortuous path in the vasculature. OCT has also been utilized to visualize the intravascular space based on differential reflectance, but most existing OCT devices rely on a rotating fiber optic which extends along the length of the device. This approach also has problems, for example, the manipulation, spinning and scanning motion required with respect to a delicate glass or polycarbonate optical fiber; the actuator mechanism located outside the patient and tip located inside the patient are significantly distant from one another, leading to inefficiencies and control issues arising from the torque created by a long, spinning member; and remote mechanical manipulation and a long spinning element distort the image due to non-uniform rotational distortion.
Additionally, current devices are mainly side-looking devices that are not able to provide valuable information to be used as guidance during invasive procedures. Forward-looking ultrasound imaging is essential in guiding an interventional device for treatment in a timely manner. For example, when implanting a heart pacemaker, electrical leads need to be implanted in precise locations. Currently there is no accurate forward-looking imaging device to direct the leads to the right locations. Thus, physicians are required to blindly rely on guide catheters and spend more time than needed when performing procedures. Also, patients are being over exposed to unnecessary radiation and toxic contrast agents involved with fluoroscopy. Given the numerous difficulties with current intravascular imaging devices, there is a need for an improved forward-looking intravascular imaging device.